Unsaturated fatty acids and oils comprising unsaturated carboxylic acids are attractive substrates for a variety of applications such as monomers for polymeric materials, as ingredients in composites, as lubricants or as fine chemicals. These materials are especially attractive since they are based on natural sources and therefore offer an environmentally and ecologically responsible route to useful chemicals. Significant effort has been devoted toward further transformations of these long chain unsaturated fatty acids to arrive at new, functional materials.
Towards this end the current invention provides a process of hydrocyanation of unsaturated and/or poly-unsaturated carboxylic acids, especially fatty acids and/or oils comprising these fatty acids to form the corresponding fatty acid/oil nitrile products. In case of the oils, typical examples are natural occurring oils, for example soybean oil. The products can be mononitriles, dinitriles and/or polynitriles. Furthermore these nitriles can be converted to the corresponding methylene-amines via a hydrogenation reaction.
Unsaturated carboxylic acids, and especially fatty acids and their derivatives containing nitrile groups are of interest as lubricants, surfactants or precursors to a variety of useful molecules. Typical examples of unsaturated fatty acids, which are naturally occurring, include mono- or polyunsaturated carboxylic acids, such as oleic acid, lauroleic acid, myristoleic acid, palmitoleic acid, linoleic acid, and arachidonic acid. Naturally occurring oils, for example soybean oil, comprise glycerin esters of these unsaturated fatty acids. Other typical useful unsaturated carboxylic acids are, for example, 3-pentenoic acid or 4-pentenoic acid.
Goertz et al. in Chem. Commun., 1521 (1997) disclosed a hydrocyanation reaction of ω-unsaturated fatty acid esters (i.e. containing a terminal olefin) using nickel phosphine catalysts. The reported yields are undesirable for commercial application. Additionally, it is known in the art that internal olefins, such as those in many naturally occurring fatty acids and esters, are more difficult to react in a hydrocyanation process than terminal olefins, such as those found in ω-unsaturated fatty acid esters.
WO 99 06358 A1 disclosed the hydrocyanation of mono-ethylenically unsaturated ester compounds to provide linear terminal nitrile molecules but did not disclose the hydrocyanation of carboxylic acids. Acidic compounds are known to deactivate catalysts and degrade typical hydrocyanation ligands.
Prior to the present invention, it was not known that unsaturated fatty acids or naturally occurring oils with olefinic unsaturation could be converted selectively in a hydrocyanation process to the corresponding fatty acid derivatives with nitrile groups in high yields. It was also not known that the so formed derivatives of fatty acids containing nitrile groups could be converted selectively in a hydrogenation process to the fatty acid derivatives with the corresponding amine groups. There is a need to access fatty acid derivatives, which have one or more additional functional groups, such as nitriles, amines, alcohols or carboxylic acids. In particular, derivatives of plant oils like soybean oil, which contain one or more additional functional groups are of interest.
Therefore, there remains a need for specific nitrile derivatives of unsaturated carboxylic acids, especially unsaturated fatty acids and/or oils of unsaturated fatty acids and a method to produce these compounds in general. There is also a need for derivatives of unsaturated fatty acids, which contain amine groups and for a method to produce such derivatives, which contain amine groups. These needs are met by the present invention.